Comparison of the effects of volatile anesthetics in varying concentrations on brain energy metabolism with brain ischemia in rats

The effects of varying concentrations and types of volatile anesthetics on neurochemical sequelae of brain ischemia were evaluated in the rat. Rats were assigned to treatment defined by a 3×3 design (anesthetic type and dose) with 5 rats/cell. Each group received halothane, enflurane, or isoflurane 0.5, 1.0, or 2.0 MAC (minimal alevolar concentration). This was followed by preischemic plasma glucose sampling, 5 min hypotension (30 mmHg) and 5 min decapitation cerebral ischemia. Preischemia plasma glucose increased with increasing anesthetic concentration and was highest in the isoflurane groups, varying from a low (±SD) of 7.19±1.79 μmol/ml in the 0.5 MAC halothane group to a high of 12.68±3.65 μmol/ml in the 2.0 MAC isoflurane group. End-ischemic brain lactate correlated with preischemic plasma glucose (r=0.5, α=0.5). We conclude that increasing concentration of volatile anesthesia with iv phenylephrine blood pressure support produces higher levels of plasma glucose and brain lactate with cerebral ischemia.